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Physicists identify upper limit to resistivity in a pure metal

Experimental atomic physicists have discovered there is a maximum amount of electrical resistance, or resistivity, that can result from collisions between electrons.

A team from the University of Toronto, L’École Normale Supérieure in Paris, and Lehigh University in Pennsylvania studied ultracold potassium atoms cooled to near absolute zero. They found that when increasing the rate at which atoms collide, the resulting resistance eventually stops increasing, offering new insights into what causes resistivity at the microscopic level.

“Electron-on-electron collisions are known to increase resistivity in some pure materials,” explains Professor Joseph Thywissen in the Department of Physics and the Centre for Quantum Information and Quantum Control in the Faculty of Arts & Science at the University of Toronto, senior author of a study published in Physical Review Letters. “The energy produced by electrical resistance shows up as heat. Transmission lines, for instance, lose up to 8% of generated electrical power. Resistivity is also interesting to study because it can be a signature of new physics in materials.”

Young disk around WRAY 15–1880 may contain a primitive planetary system

Italian astronomers have used the Very Large Telescope (VLT) to perform polarimetric observations of the star WRAY 15–1880 and its young circumstellar disk. Results of the new observations, presented June 10 on the arXiv preprint server, suggest that this disk may host a primitive planetary system.

Circumstellar disks are accretion disks orbiting stars, composed of gas, dust, planetesimals, asteroids or collision fragments. Around the youngest stars, they are the reservoirs of material out of which planets may form.

At a distance of some 492 light-years from Earth, WRAY 15–1880 (also known as RX J1842.9–3532) is a solar-type classical T Tau star in the CrA-North subregion of the Corona Australis (CrA) complex. It has a mass of around 1.24 solar masses and is estimated to be 2.8 million years old.

Data suggest ‘red flag’ laws are linked to sustained reductions in arrests

Individuals subject to extreme risk protection orders (ERPOs), or “red flag” laws, were significantly less likely to be arrested—including for violent and firearm-related offenses—while the orders were in effect than in the six months before. Strikingly, the drop in arrests did not end when the orders expired and continued for months afterward, according to a new study published in PNAS Nexus.

“These findings suggest ERPOs may interrupt acute-risk behavior while also contributing to longer-term reductions in criminal activity,” said Veronica Pear, first author of the paper. Pear is an epidemiologist and assistant professor at the UC Davis Centers for Violence Prevention (CVP).

Intermolecular collisions may explain why organic radical fluids become unusually magnetic

Certain substances can become magnetic when exposed to an external magnetic field. Magnetic susceptibility measures how easily a material can be magnetized. Materials known as organic radicals have been noted to possess anomalously large magnetic susceptibility. However, researchers have been unable to explain this phenomenon using conventional theories.

Now, researchers at the University of Osaka have developed a theoretical framework to explain this anomalous magnetic susceptibility. This discovery was recently published in the Journal of Physical Chemistry Letters.

Rare B meson decays tighten search for hidden particles and dark matter links

A University of Melbourne researcher has placed the strongest constraints yet on certain rare decays of subatomic particles, narrowing the window for where new “hidden” particles could be lurking.

In research published in Physical Review Letters, Dr. Daniel Marcantonio analyzed data from the Belle experiment to search for “feebly interacting particles” (FIPs)—a broad class of hypothetical particles that interact extremely rarely with ordinary matter.

FIPs are predicted by many theories that extend our current understanding of particle physics, and some could serve as candidates for dark matter or as messengers between ordinary matter and a hypothetical “dark sector.”

A heat sensor for living cells could offer new views of cell metabolism, rapid antibiotic testing

When living cells grow, divide or respond to drugs, they give off tiny amounts of heat that offer information about what the cells are doing. But because these heat signals are so vanishingly small, they have traditionally been impossible to measure directly. Researchers in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a calorimeter—a device that measures the heat transfer between a living system and its environment—that can detect metabolic heat signals on the order of 100 picowatts, or trillionths of a watt, in living cells.

The device is the most sensitive of any comparable bio-calorimeter to date. The new “pico-calorimeter” can track the metabolism of small populations of bacteria in real time, as well as monitor how bacterial growth changes in response to different antibiotics.

The work is from the lab of Joost Vlassak, the Abbott and James Lawrence Professor of Materials Engineering, and was carried out by Harvard associate Juanjuan Zheng, a former postdoctoral researcher in Vlassak’s lab. The research is published in the Proceedings of the National Academy of Sciences.

High degree of quantum entanglement detected for first time in centimeter-sized crystal of strange metal

Many quantum effects can be observed only when a small number of particles is studied—individual atoms, molecules or photons, for example, carefully shielded from the rest of the world. But what about macroscopic objects, consisting of an unimaginably large number of particles? Can they, too, display effects that provide a direct glimpse into the quantum world?

Experimentalists at TU Wien have now shown that this is possible: A centimeter-sized crystal of a so-called strange metal was investigated, and a high degree of quantum entanglement was detected. This was made possible by a clearly defined method from quantum information theory: the quantum Fisher information.

It establishes a new bridge between solid-state physics and quantum physics: Quantum entanglement can be directly quantified in a macroscopic strange-metal material. The paper is published in the journal Nature Physics.

Nanomedicine discovery uses salt to overcome major obstacle in gene therapy

Researchers at the University of Houston’s College of Pharmacy have discovered an unexpectedly simple strategy to improve the performance of mRNA vaccines and gene therapeutics: adding salt. The findings, published in Small, address one of the biggest challenges facing modern gene medicine—getting fragile therapeutic material to the right place inside cells.

“We are introducing salt-loaded lipid nanoparticles as a novel and broadly applicable design principle for gene delivery,” said Fanfei Meng, assistant professor and Presidential Frontier Faculty member in the Department of Pharmacological and Pharmaceutical Sciences. “What makes this exciting is that we can significantly improve delivery efficiency without needing to invent entirely new materials.”

Lipid nanoparticles, or LNPs, are tiny fat-based delivery vehicles widely used to transport fragile genetic material into cells. They became widely recognized during the COVID-19 pandemic through mRNA vaccines developed by Moderna and Pfizer. Today, scientists are also using LNPs to develop new treatments for cancer, rare diseases and genetic disorders.

Quantum hyperdimensional computing can work 500 times faster than other methods

Cleveland Clinic researchers are unlocking quantum computing’s full potential through the creation of a new computing paradigm inspired by the human brain. Fabio Cumbo, Ph.D., research associate in the lab of Daniel Blankenberg, Ph.D., associate staff, Computational Life Sciences, is developing the model, called quantum hyperdimensional computing (QHDC).

Cumbo published the first-ever implementation of QHDC in two distinct experiments in npj Unconventional Computing.

Hyperdimensional computing (HDC) is a type of computing based in neuroscience. It follows the idea that a concept in the brain is not stored on one single neuron. For example, when you think of a cat, there is no single neuron in your brain solely responsible for knowing what a cat is. That information is spread across thousands or millions of neurons, so if one neuron fails, you still remember what a cat is.

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